Radio frequency signal modifying apparatus for pressurized transmission systems



Jan. 9, 1962 s. SCHNEIDER 3,016,500

RADIO FREQUENCY SIGNAL MODIFYING APPARATUS FOR PRESSURIZED TRANSMISSION SYSTEMS Filed Jan. 18, 1960 Tial. 15 l4 /6 I L l l //I l J 14 LPRESSURIZED soup LPRESSURIZED GAS D\ELECTRIC GAS Tic. Z.

(.l RCUIT COMPONENT TicTEu.

CIRCUIT COMPONENT INVENTOR. SEW/100A SC/vWf/DE? ATTORNEYS United States Patent "ice poration of New York Filed Jan. 18, 1960, Ser. No. 3,110 4 Claims. (Cl. 333--34) The present invention relates to apparatus including a pressurized radio frequency transmission line and a radio frequency circuit component which constitutes a barrier to the pressurizing medium in the transmission line arranged in such a way that separate physical paths are provided for the radio frequency energy and the pressurizing medium so that the system comprises a unitary pressurized system..

It is frequently desirable in the transmission of radio frequency power and particularly in the transmission of microwave frequency power to fill the coaxial cable, the waveguide, or other transmission line with a gas under pressure. In some instances it may be desired to employ a pressurized liquid. It will be understood that throughoutthis specification and in the claims the term pressurized includes both positive and negative pressure, that is, pressures higher than normal atmospheric pressure or partial or near vacuums with respect to atmospheric pressure. One important reason for the use of pressurization may be to exclude moisture from the transmission line; the presence of moisture can have a very detrimentaleifect upon the characteristics of such a transmission line. Filling the line with dry gas under moderate pressure is a very efiective method of minimizing moisture within a transmission line. Although pressurization is particularly useful in transmission systems carrying large quantities of power, it is not limited to such applications.

' It will often be desired to insert electrical circuit elements in series in a transmission line of the pressurized type. For example, it may be desirable to insert a filter or to insert an amplifier or some other circuit component. While it may be possible in some instances to design filters or certain other circuit components which would not impede the passage of the pressurizing medium within the transmission line and the operation of which would riot be seriously affected by the presence of the pressurizing medium, nevertheless, in many instances it may be desirable to utilize a circuit component in the transmission line which is of a type that would create a barrier to the pressurizing medium.

Heretofore the insertion of an inpenetrable, electrical circuit component in series in a pressurized transmission line would require that separate pressurization systems be maintained on either side of the circuit component. This is obviously an undesirable situation. Such a situation would be particularly troublesome in' installations where-it was desired to circulate the pressurizing medium for cooling purposes.

' "llie present invention provides means of particularly simple and efiicient form allowing the utilization of inpentrable circuit components inserted in the middle of a pressurized radio frequency transmission line without creating a discontinuity in the pressurization system; 'It will be understood that the electrical compouents described as inserted in the middle or in series the trans-' mission line may actually be electrically in parallel across.

the transmission line.

In addition to the above described features and advantages of the invention, it is an object of the invention to provide apparatus whereby an electrical component 3,016,500 Patented Jan. 9, 1962 can be inserted in the middle of a radio frequency trans mission line of the pressurized type without creating a discontinuity in the pressurization of a transmission line.

It is a further object of the present invention to provide apparatus of the foregoing type wherein the introduction of the electrical circuit component results in relatively little resistance to the flow of the pressurizing medium. g

It is a still further object of the present invention to provide apparatus of the foregoing type wherein the presence of a path for the pressurizing medium results in no significant detrimental effect on the electrical characteristics of thetransmission line.

Other objects and advantages will be apparent from a consideration of the following description in conjunction with the appended drawings in which:

FIGURE 1 is a vertical, sectional view of a portion of a cylindrical, coaxial, radio frequency transmission line incorporating the present invention;

FIGURE 2 is a partially schematicvertical' sectional view of an alternative form of the invention for use in rectangular waveguide transmission line; and

FIGURE 3 is a partially schematicv vertical sectional view of a further alternative embodiment of the invention also adapted for use in conjunction with rectangular waveguide transmission line.

Referring now to FIGURE 1, a section 11 of cylindrical coaxial transmission line is shown comprising an outer conductor 12 and an inner conductor 13. The transmission line section 11 incorporates a radio frequency electrical filter according to the present inven tion, which does not interfere with pressurization of the transmission line as a unitary system.

.The space between the inner-conductor 13 and the outer-conductor 12 in the filter section is filled with a solid dielectric 14. In other cases the circuit element introduced in the transmission line may be filled with oil, cooling liquid, or may have an evacuated portion which would normally block the passage of the pressurizing medium in the line 11.

In FIGURE 1, the normally solid center conductor 13 is provided with a longitudinal opening 15 extending through the portion of the transmission line section 11 containing the solid dielectric 14. Ports 16 and 17 are provided at either end of the opening 15 so that a passage for the pressurizing medium in the transmission line 11 is provided through the filter section filled with dielectric The electrical filter may take many forms, but is illustrated as comprising three cylindrical enlargements 18 of the center conductor 13. While the arrangement of FIGURE 1 is shown as applied to a system wherein a filter is inserted in the transmission line, the same techniques could be applicable to the insertion of other circu it components such as amplifiers, attenuators, switchports on each end could be substituted for the larger ports 16 and 17 whichxar'e shown.

An alternatiyearrangement is" illustrated in FIGURE 2' which is particularly adapted for use in rectangular waveguide. The arrangement of FIGURE 2 couldalso be adapted for use with cylindrical vt'aveguide. The transmission line section 21, in FIGURE 2, cornprises a straight transmission line section 22, and a branch transmission line including a first curved section 23 of coaxial form having a center conductor 24 and a second curved section of coaxial transmission line 27 having a center conductor 28. The branch transmission line is completed electrically by a circuit component 26 which may be a filter as illustrated in FIGURE 1 or some other circuit component such as an amplifier or the like. Suitable transition structures 25 and 29 are provided for joining the branch transmission line to the straight transmission line 22.

Electrical transmissionbarriers or walls 31 are provided in the straight transmission line section 22. These barriers are provided with openings 32 which may be of circular cross-section to allow passage of the pressurizing medium through the straight transmission line section. The openings 32 are of a size to constitute a waveguide beyond cut-off for the frequencies transmitted through the transmission line 21. It will be understood that the transition structures 25 and 29 are shaped so that they do-not substantially impede the flow of the pressurizing medium. In the embodiment shown these structures will be of substantially conical form.

In FIGURE 2 a radio frequency signal impinging at 29 in the waveguide section 21 will be guided by the transition structure 25 into the curved coaxial transmission line 23. Substantially none of. the energy will be transmitted through the barriers 31; these barriers will also preferably be placed and designed to minimize reflections back toward theorigin of the radio frequency signal. The radio frequency signal will be transmitted through the circuit component 26, where it will be modified in some fashion depending on the nature of the circuit component and will return by. means of the curved coaxial transmission line section 27 to the transition structure 29 which will serve to guide it into the straight transmission line section 22, preferably with a minimum of reflection or attenuation. The radio frequency signal will then be available at 30, for whatever utilization may be desired.

FIGURE 3 is still another variation of the invention in which the transmission line section 41 comprises two waveguide sections 42 and 44 joined by a conduit 43 which is dimensioned at least in the vicinity where it joins the waveguides sections 42 and 44 as a waveguide beyond cut-off for the frequencies to be transmitted in the apparatus;

The radio frequency signal, is transmitted in a manner similar to that described withreference to FIGURE 2 through a transition structure 47 to a coaxial line section 45 having a center conductor 46, thence through a circuit component 48 which may be aifilter, amplifier or other circuit component and through coaxial line section 49 having an inner conductor 51, and through transition structure 52 to waveguide section 44.

Wayeguide sections 42 and 44 may be provided with appr dp riate extensions 53 and 54 extending past their junction with the coaxial line sections 45 and 49, and theseextensions 53 and 54 may be dimensioned to minimize unwanted reflections from the junction ofthe respective waveguide sections 42 and 44 with the fluid con duit' 43.

-From the foregoing explanation it will be seen that a remarkably simple and efiicient structure is provided whereby a circuit component can be included in a section of radio frequency transmission line without -intro ducing a disconti'nuity in the transmission line which would interfere with the fiow of the pressurizing medium therethroug-h. 'It' will bev appreciated that in addition to the several variationsof the: invention describedand suggested, that many other variations will be obvious to those' of ordinary skill. in the art. Accordingly it is desired that the, scope: of the-invention not be limited to those limited signal comprising a first coaxial radio frequency transmission line section, a circuit component for modifying said signal and incapable of transmitting a pressurizing medium, said component being connected to receive an input signal from said first transmission line section, a second coaxial radio frequency transmission line section connected to receive an output signal from said circuit component, a first pressurizable transmission line connected to said first coaxial transmission line section, a second electrically separate pressurizable transmission line connected to said second coaxial transmission line section, at least one aperture in each of said pressurizable transmission lines dimensioned to be beyond cutoff as to transmission of signals within the operating frequency range of said system, and a conduit connecting the apertures in the respective pressurizable transmission lines to provide a closed path for pressurizing medium therebetween.

2. An electrical system for modifying a radio fre-. quency signal comprising a first pressurizable radio frequency transmission line section, a circuit component for modifying said signal and incapable of transmitting a pressurizing medium, said component being connected to re ceive an input signal from said first transmission line sec-. tion, a second pressurizable radio frequency transmission line section connected to receive an output signal from said circuit component, a first rectangular waveguide connected to said first transmission line section, a second electrically separate rectangular waveguide connected to said second transmission line section, at least one aperture in each of said waveguides dimensioned to .be beyond cutoff as to transmission of signals within the op-. erating frequency range of said system, anda conduit connecting the apertures in the respective waveguides to provide a closed path for pressurizing medium between. said waveguides.

3. An electrical system for modifying a radio frequency signal comprising a first coaxial radio frequency transmission line section, a circuit component for modifying said signal and incapable of transmitting a pressurizing medium, said component being connected to receive an inputsignalfrom said first transmission line section, a second coaxial radio frequency transmission line section connected to receive an output signal from said'circuit component, a first pressurizable rectangular waveguide connected to said first coaxial transmission line section, a second electrically separate pressurizable rectangular waveguide connected to said second coaxial transmission line section, at least one aperture in each of said wave guides dimensioned tobe beyond cutoff as to transmission of signals within the operating frequency range of said system, and a conduit connecting the apertures in the respective waveguides to provide a closed path for pres-- surizing medium between said Waveguides. i

4. An electrical system for modifying a radio frequency signal comprising a first coaxial radio frequency transinput signal from said first transmission line section, a second coaxial radio frequency transmission line section connected to receive an output signal from said circuit; component, a waveguide electrically connected to said first and second transmission line sections, a wall of con,

ductive material in said waveguide between points of com nection of said transmission line sections therewith and at least oneaperture in said wall dimensioned to be beyond cutoff as to transmission of signals-within the operating. frequency. range of said system.

References Cited in the file ofthis, patent UNITED STATES PATENTS. 

